1. Multiplication and Division
Assembly Language

2. Multiplication Use of AX and DX is necessary Byte × Byte Word × Word
Word × Byte

3. Byte × Byte One of the operand must be in AL
Second can be register/memory
Result in AX
Example-1
MOV AL, 25H
MOV BL, 65H
MUL BL
MOV myresult, AX

4. Example-2
MOV AL, DATA1
MUL DATA2
MOV myresult, AX

5. Word × Word One of the operand must be in AX
Second can be register/memory
Result in DXAX
Example-1
DATA3 DW 2387H
DATA4 DW 2F79H
result 1 DW 2DUP(?)
MOV AX, DATA3
MUL DATA4
MOV RESULT1, AX ;store lower result
MOV RESULT1+2, DX ;store higher result

6. Word × Byte Similar to word × word AL contains the byte operand
AH must be zero
DATA5 DB 6BH
DATA6 DW 12C3H
Result3 DW 2DUP(?)
MOV AL,DATA5
SUB AH,AH
MUL DATA6
MOV [BX], offset result3
MOV [BX], AX
MOV [BX]+2, DX

7. Unsigned Multiplication Summary
Operand 1
Operand 2
Result
Byte x byte AL
Reg/memory AX
Word x word
DX:AX
Word x byte
AL=byte, AH=0

8. Unsigned Division Summary
Multiplication
Numerator
Denominator
Quotient
Remainder
Byte / byte
AL=byet, AH=0
Reg/memory AL AH
Word / word
AX=word,DX=0 AX DX
Word / byte
AX=word
Double word/word
DXAX= double word

9. Byte/Byte Denominator can not be immediate Example-1 MOV AL,DATA
SUB AH,AH
DIV 10
MOV AL, DATA1
DIV DATA2
MOV quot, AL
MOV remain, AH

10. Word/Word
MOV AX,10050 SUB DX,DX MOV BX,100 DIV BX MOV quot, AX MOV remain,DX

11. Word/Byte
MOV AX, 2055 MOV CL, 100 DIV CL MOV quot, AL MOV remain, AH